<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <style>
        * {
            padding: 0;
            margin: 0;
        }

        li {
            list-style: none;
        }

        img {
            vertical-align: top;
        }

        body {
            color: #4e4e4d;
            font-size: 12px;
            line-height: 22px;
        }

        .a {
            height: 58px;
            width: 1145px;
            background-color: #91271c;
            margin: auto;
        }

        .a h1 {
            width: 132px;
            height: 18px;
            float: left;
            /* background-color: #ff0; */
            margin-left: 70px;
            margin-top: 20px;
            color: #fff;
        }

        .a ul {
            float: left;
            width: 510px;
            height: 58px;
            background-color: #ff0;
            margin-left: 155px;
        }

        .a ul li {
            /* 宽度被内容撑开 */
            float: left;
            margin-right: 42px;
            line-height: 20px;
            margin-top: 23px;
        }

        .on {
            border-bottom: 1px solid #000;
        }
    </style>
</head>

<body>

    <div class="a">
        <h1>redddd</h1>
        <ul>
            <li>首页</li>
            <li class="on">关于我们</li>
            <li>我们的服务</li>
            <li>客户案例</li>
        </ul>
    </div>


</body>

</html>